docs: def convert_none(key, val, attr_type, attr={}, cdata=False):
      """Converts a null value into an XML element"""
      LOG.info('Inside convert_none(): key="%s"' % (unicode_me(key)))
  
      key, attr = make_valid_xml_name(key, attr)
  
      if attr_type:
          attr['type'] = get_xml_type(val)
      attrstring = make_attrstring(attr)
      return '<%s%s></%s>' % (key, attrstring, key)